Rotary piston machines

ABSTRACT

Rotary piston machines have a casing with two intersecting cylindrical bores in which a main rotor and a gate rotor are mounted to rotate. Each rotor has a hub and one tooth with a concave flank extending from the hub and a recess adjacent said flank, said flank and recess of the gate rotor being generated by the main rotor tooth so that when the rotors rotate the main rotor tooth moves in sealing proximity along the gate rotor concave tooth flank and the gate rotor recess. Together with the walls of the bores the rotors provide chambers which change volume during the rotation. The rotors have hub portions with constant radius which is greater on the gate rotor hub and provide large axial inlet and outlet ports for an elastic working fluid.

United States, Patent [191 Arnegard et al.

p [1111 r 3,799,712 Mar. 26, 1974 ROTARY PISTON MACHINES [73] Assignee: Atlas Copco Aktiebolag, Nacka,

Sweden [22] Filed: Oct. 24, 1972 [21] App]. No.: 300,103

Related U.S. Application Data [63] Continuation of Ser. No. 46,664, June 16, 1970,

Primary Examiner--Carlton R. Croyle Assistant Examiner-John J. Vrablik Attorney, Agent, or Firm-Eric Y. Munson 57] ABSTRACT Rotary piston machines have a casing with two intersecting cylindrical bores in which a main rotor and a gate rotor are mounted to rotate. Each rotor has a hub and one tooth with a concave flank extending from the hub and a recess adjacent said flank, said flank and recess of the gate rotor being generated by the main rotor tooth so that when the rotors rotate the main rotor tooth moves in sealing proximity along the gate rotor concave tooth flank and the gate rotor recess. Together with the walls of the bores the rotors provide chambers which change volume during the rotation. The rotors have hub portions with constant radius which is greater on the gate rotor hub and provide large axial inlet and outlet ports for an elastic working fluid.

5 Claims, 7 Drawing Figures PATENTEUHARZS I974 SHEET 1 OF 6 BO OLOF ROLAND ARNEGARD, KAJ BENGT INGEMAR EMANUELSSON and HANS KRISTGFFER OLOFSSON INVENTOR'S 7 MUNSON 8 FIDDLBR,

Attorneys.

MR 2 6 HM sum 2 [IF 6 BO OLOF ROLAND ARN KAJ BENGT INGEMAR EMANUE EGARD LSSON .and

SO TO HANS KRISTOFFER OLOFS N INVEN Rs MUNSON & FIDDLER Attorneys.

mmmmzs 1974 I 7 3799712 sum 3 OF 6 I v i BO OLOFHROLAND ARNEGARD, KAJ BENGT INGEMAR EMANUELYSSON and HANS KRISTOFFER OLQFSSON INVENTORS BY MUNSON'81FIDDLER,

- Attorneys.

SHEET u BF 6 7 BO OLOF ROLAND ARNEGARD,

KAJ BENGT INGEMAR EMANUELSSON and I HANS KRISTOFFER OLOFSSON INVIz'Nl'OKS BY MUNSON & FIDDLER,

Attorneys MEHTEUM BO OLOF ROLAND ARNEGARD,

KAJ BENGT INGEMAR EMANUELSSON and HANS KRISTOFFER OLOFSSON [NVENTORS BY MUNSON & FIDDLER,

Attorneys.

PAHIitTEBl-mms m4 7 7 sum 6 OF 6 BO OLOF ROLAND ARNEGARD,

KAJ BENGT INGEMAR EMANUELSSON 25 and HANS KRISTOFFER OLOFSSON IN VENTURE BY MUNSON a. FIIJDLER Attorneys.

ROTARY PISTON MACHINES This application is a continuation of copending application Ser. No. 46,664 filed June 16, 1970, now abandoned.

This invention relates to rotary piston machines having a main rotor and a gate rotor provided each per se with a hub having a hub portion with substantially constant radius and with a tooth, said tooth on the main rotor having a concave flank and a convex flank, said convex flank merging into said hub portion of the main rotor, said tooth on the gate rotor having at least a concave flank and a second flank, said second flank merging into the hub portion of the gate rotor, said hub on the main rotor having a recess adjacent said concave flank of the main rotor tooth for the passage of the gate rotor tooth, said hub on the gate rotor having a recess adjacent said concave flank of the gate rotor tooth for the passage of the main rotor tooth, and said machine having a casing with intersecting cylindrical bores, one for each rotor, and end walls formed with axial inlet and outlet ports for an elastic working fluid, said rotors being mounted for rotation in said bores in said casing for positive displacement and change of volume of quantities of working fluid moving through the machine at each working cycle, and said machine having means for synchronizing the rotation of the rotors.

One object of this invention is to provide a rotary piston machine of this type which is easy to manufacture. Another object of this invention is to provide a rotary piston machine of this type which has high capacity in relation to the external dimensions of the machine and particularly the machine casing. A further object of the present invention is to provide a rotary piston machine of the type described in which the length of the leakage of sealing lines as compared with the swept cylinder volume of the machine is a minimum. A still further object of the invention is to provide in rotary piston machines of the type described inlet and outlet ports which are as large as possible. A further object of the invention is to provide a rotary piston machine of the type described in which the velocity of the working fluid in the machine and in the in and outlet ports is low. A still further object of the invention is to provide a rotary piston machine of the type described which has relatively large intake volume. A still further object of the invention is to provide a rotary piston machine with low discharge temperature of the discharged working fluid when the machine is operated as a compressor.

The rotary piston machine of the type described hereinabove is substantially characterized by the fact that the substantially constant radius of the main rotor hub portion is materially less than the substantially constant radius of the gate rotor hub portion which controls the axial port in the end wall of the gate rotor bore.

The machine is further characterized by the fact that the substantially constant radius hub portion of the gate rotor controlling the high pressure port'merges through a continuously convex contour portion with a concave contour portion adjacent the gate rotor tooth and that said contour portions define the gate rotor recess and together with the concave gate rotor tooth flank from a contour with a single inflection point, which simplifies manufacture.

The invention is also characterized by one or more of the features set forth in the appended claims. The rotary piston machine according to the invention is primarily intended to operate as a compressor but may also be carried out so as to operate as a motor. In the accompanying drawings one embodiment of a rotary piston machine according to the invention carried out as a compressor is illustrated by way of example together with a modification.

FIG. 1 is an end view of a rotary piston compressor according to the invention with one tooth on each rotor.

FIG. 2 is a cross section of the compressor in which, however, the rotors are illustrated in end view.

FIG. 3 is a longitudinal axial section on a plane through the rotor axes on line III-III in FIG. 1.

FIG. 4 is an end view of the cooperating main and gate rotors of the machine in FIGS. l-3.

FIGS. 5 and 6 are detail views on a reduced scale somewhat diagrammatically illustrating the rotors and contours of the cylinder bores, as viewed from one end of the rotors in the moment when compression starts and the moment when discharge starts, respectively.

FIG. 7 is a view similar to FIG. 4 with the two rotors in a position where the tooth tips of the rotors have just met, said rotors being somewhat modified with regard to the rotors illustrated in FIGS. 2 and 4-6.

The rotary piston machine illustrated in FIGS. 1-7 is a single stage tooth compressor provided with a main rotor and a gate rotor each per se provided with one tooth. The machine is provided with a casing which consists of a central compressor housing 1 provided with two end walls 2, 3 which are bolted to the central compressor housing 1 by means of bolts 4. The housing 1 is provided with two cylindrical intersecting bores 5, 6 with parallel axes which bores intersect to a certain degree. The bores 5, 6 and end walls 2, 3 form working chambers for a main rotor 7 and :a gate rotor 8 which rotors are provided and secured on parallel shafts 9 and 10, respectively, which are mounted for rotation in bearings in the end walls 2, 3 and synchronized by means of a toothed gear transmission 12 and sealed towards the working chambers in the housing 1 by sealing rings 13. The housing 1 is provided with an inlet conduit portion 14 and an outlet conduit portion 15 which two portions end up in planes 16 and 17 which are perpendicular one to the other and parallel with the rotor axis. A passage 18 from the conduit portion 14 leads through the end walls 2 and 3 and the housing 1 to inlet ports for the working chamber of the machine which inlet port consists of a radial inlet port portion 19 and two axial inlet port portions 20 one in each end wall. The outlet conduit portion 15 is through an outlet passage 21 in the housing 1 and the end walls 2, 3 connected to two axial outlet ports 22 one in each end wall. The housing 1 is air cooled and the end walls 2, 3 are liquid cooled and are for this purpose provided with liquid cooling fluid passages 23 and passages 24 for draining cooling fluid from the transmission housing 34.

The main rotor 7 has a hub with a hub portion 25 with constant radius which in the illustrated embodiment extends through an angle of 225 of the periphery of the main rotor hub. The main rotor hub, furthermore, carries a tooth 26 which has a leading convex flank which is formed by a flat portion 27 which connects the hub portion 25 with constant radius with a preferably circularly arcuate portion 28 which extends to the tip 29 of the tooth. The trailing flank of the main rotor tooth 30 is concave and disposed immediately adajacent a recess 31 which is formed in the hub and extends to and merges into the hub portion 25.

The main rotor 7 has a cavity 32 which extends into the main rotor from an opening 33 in the trailing concave flank 30 of the main rotor tooth, said opening extending over the main part of said flank. The cavity 32 is shaped in such a manner that the main rotor is dynamically and naturally also statically balanced.

The relation between the constant radius of the hub portion 25 of the main rotor and the maximum radius of the main rotor tooth 26 is in the illustrated embodiment 35 to 60. Preferably, the maximum radius of the main rotor tooth may be 50 to 100 per cent larger than the constant radius of the hub portion 25 of the main rotor. The length of the main rotor may preferably be substantially equal to the maximum radius. The invention results in a very favourable utilization of the volume of the compressor casing. Furthermore, a favourable relation between the total sealing line length and the swept volume of the machine is obtained which involves small leakage losses.

The gate rotor 8 has a hub with a hub portion 35 with constant radius which in the illustrated embodiment extends over an angle of 225 of the periphery of the gate rotor and cooperates with the hub portion 25 with constant radius of the main rotor and seals against said protion. However, upon rotation of the rotors the peripheral speed of the main rotor hub portion differs from the peripheral speed of the gate rotor hub portion. This difference causes a suitable wear of the rotor surfaces which results in a suitable sealing clearance. The gate rotor has a tooth 36 with a leading concave flank 37 generated by the tip 29 of the tooth 26 of the main rotor during the movement of said tip from the tip 38 of the gate rotor tooth to the root of said tooth. The leading flank of the gate rotor tooth 36 merges at the root of the tooth in a portion 39 which is an envelop to the ends of the radii of a family of circles generated by the circular arch shaped portion 28 of the main rotor tooth on the gate rotor. The envelop portion 39 merges 1 into the hub portion 35 via a portion 40 which is generated by the portion 27 of the main rotor tooth and which is consequently an envelop of a family of lines. The gate rotor tooth 36 has a portion 41 at the tooth tip which is shaped as a circular arc and extends from the tip 38 of the tooth and merges into the trailing flank 42 of the gate rotor which is a tangent to the hub portion 35 and may have any suitable shape within certain limits, since it does not have to form a seal with the main rotor. The tips 38, 39 of the tooth may be rounded as obvious from FIG. 7 so that they are not so easily damaged and produce .a better seal with the respective cooperating rotor portion. The tip 38 of the gate rotor tooth, the circularly are shaped portion 41 and the trailing flank 42 have generated the trailing flank 30 of the main rotor and the recess 31 in the main rotor hub but these portions which extend over an arc of 45 of the rotors do not have to form a seal together.

Since the gate rotor is also asymmetric it has, similarly to the main rotor, been provided with a cavity 43 which extends into the gate rotor from an opening 44 in the trailing flank 42 of the gate rotor tooth. The effective height of the gate rotor tooth is in the illustrated embodiment about one third of the effective height of the main rotor tooth. By this arrangement and this relation between the heights of the teeth it is possible to carry out the outlet ports so large that the air or gas velocity in these ports stay within reasonable limits and the flow velocities are thereby kept down. Similarly more suitable fluid velocity is obtained in the passages which surround the rotor in the compressor housing.

In order to make this operation of the machine more obvious and clear, the rotors in FIGS. 5 and 6 have been illustrated in the positions which they take when the compression starts as in FIG. 5 and when the discharge starts as in FIG. 6. FIG. 7 which illustrates the modification with rounded rotor tips also illustrates the position of the rotors at the moment when the tips 29, 38 meet. The distance or gate rotor radius to the sealing line between the tip 29 and the flank 37 should in all positions of the rotors be larger than the radius to the sealing line between the convex flank 27, 28 and the hub portion 40, so that the torque of the fluid pressure on the gate rotor tooth is always positive. The direction of rotation of the rotors is illustrated by arrows in FIGS. 1, 2, 5 and 6 and is the same also in FIGS. 4 and 7. FIG. 7 illustrates the rotors in the position they take when the tip 29 and 38 of the rotor teeth have just arrived into cooperating position where the tooth tip 29 starts to sweep the surface 37 of the tooth 36 in sealing proximity the clearance at the tooth tip 29 in FIG. 7 being somewhat exaggerated. In order to improve the sealing around the rotors, the convex peripheral sur- 1 faces of the rotors may preferably be provided with a coating of a material which may be partly worn away, for instance paint. The end surfaces or end walls of the cylinder bores which are directed towards the rotors may also be provided with such surface coating.

The rotor machines described hereinaboveshould only be considered as examples and may be modified and varied in several different ways within the scope of the following claims.

We claim:

1. In a rotary piston machine for handling a working fluid, comprising the combination of:

a. a main rotor and a gate rotor each of said rotors having a hub portion of substantially constant radius and provided with a single tooth extending radially from said hub portions;

b. a casing having intersecting cylindrical bores rotatably supporting each of said rotors;

0. each of said bores being defined by end walls having inlet and outlet ports for the working fluid, at least one of said ports being axial and located in one of said end walls;

(I. said rotors being rotatable in opposite directions in said bores for positive displacement and change of volume of working fluid moving through the machine during each working cycle and in close sealing proximity to the end walls of the respective bores;

e. the tooth on the main rotor having a tip and a first flank and a second flank, the second flank merging with the constant radius hub portion of the main rotor;

f. said tooth on the gate rotor having at least one concave flank generated by the main rotor tip and a second flank merging with the constant radius hub portion of the gate rotor;

g. the hub portion of the main rotor having a recess adjacent the said first flank of the main rotor tooth to permit passage of the gate rotor tooth;

h, the hub portion of the gate rotor having a recess adjacent the concave flank to permit passage of the main rotor tooth;

. the substantially constant hub radius of the main rotor hub portion being shorter than the substantially constant hub radius of the gate rotor hub portion;

j. said gate rotor hub portion being effective to control an axial port in the end wall of the gate rotor bore;

k. said port acting as a high pressure port and being substantially are shaped and extending along a sweep of at least 60 and radially to a distance shorter than the gate rotor hub portion to provide a sealing means around said port during the portion of the gate rotor revolution when the port is closed by the gate rotor hub portion;

1. the constant radius portion of the main rotor extending about a sweep between 180 and 250 of its pitch circle;

m the second flank of the main rotor comprising a convex flank portion and a substantially straight portion which is tangent to the constant radius hub portion and said convex flank portion which extends substantially to the maximum radius of the main rotor tooth,

n. the rotors having such profiles as to seal the bores and the end walls of the casing during the main part of each revolution and so as to cause the concave flank of the gate rotor tooth and said recess defining convex and concave contour portions to be generated by said main rotor tooth and the convex flank thereof along a sweep of substantially 90 of the periphery of the gate rotor, the concave flank of the gate rotor tooth and said convex and concave contours forming together combined concave and convex contour portions having a single inflection point.

2. A rotary piston machine according to claim 1, in

which the profiles of said rotors being calibrated so that a compressed fluid space communicating with the high pressure port will be located between the concave flank of the gate rotor tooth and the convex flank of the main rotor tooth when the teeth interengage and said sealing lines move and until the sealing lines intersect, whereby the torque of the fluid pressure acting on said rotors during each revolution is maintained in the same direction during a complete working cycle of the machine.

3. A rotary piston machine according to claim 1 in which the gate rotor tooth comprises a straight portion which is tangent to the constant radius hub portion and merges with the leading flank of the gate rotor tooth through an arcuate portion forming the maximum radius of the gate rotor tooth.

4. A rotary piston machine according to claim 3 in which the gate rotor hub recess comprises a first concave portion which forms an envelope for the ends of the radii of a family of circles generated by the convex flank portion of the main rotor tooth, and a second convex portion which is generated by the movement of the tangent point between the straight portion of the main rotor tooth and said convex portion of the gate rotor hub recess.

5. A rotary piston machine according to claim 3 in which the port acting as high pressure port is substan-- tially are shaped and extends along a sweep of at least 60;is confined radially substantially by a first outer are disposed at a distance from the rotor axis which is shorter than the gate rotor hub portion radius to provide an outer axial sealing area along said port during the portion of the gate rotor revolution when the port is closed by the gate rotor hub portion and a second inner are disposed at a distance from the rotor axis which is larger than the radius of the rotor shaft and provides an inner axial sealing area broader than said outer axial sealing area, said high pressure port being confined at one end by an edge along a line substantially defined by the tip of the main rotor tooth during a substantial portion of its sweep along the concave rotor tooth flank.

, :UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION fatent No. 3-799 r Dated March 26, 1974 B0 Olof Roland Arnegard, Kaj Benqt Inqemar Emanuel- Inventofl -esnnr and flans lizismfier m- It is certified that error appears in the nbove-identified patent and that said Letters Patent are hereby corrected as shown below:

[30} Foreign Application Priority Data June 18, 1969 Sweden.............8636/69 (SEAL) Attest:

MCCOY M. GIBSON JR. Attesting Officer C. MARSHALL DANN Commissioner of Patents USCOMM-DC 603764 69 FORM PO-105O (10-69) u 5. GOVERNMENT PRINTING OFFICE: I969 o-sea-au, 

1. In a rotary piston machine for handling a working fluid, comprising the combination of: a. a main rotor and a gate rotor each of said rotors having a hub portion of substantially constant radius and provided with a single tooth extending radially from said hub portions; b. a casing having intersecting cylindrical bores rotatably supporting each of said rotors; c. each of said bores being defined by end walls having inlet and outlet ports for the working fluid, at least one of said ports being axial and located in one of said end walls; d. said rotors being rotatable in opposite directions in said bores for positive displacement and change of volume of working fluid moving through the machine during each working cycle and in close sealing proximity to the end walls of the respective bores; e. the tooth on the main rotor having a tip and a first flank and a second flank, the second flank merging with the constant radius hub portion of the main rotor; f. said tooth on the gate rotor having at least one concave flank generated by the main rotor tip and a second flank merging with the constant radius hub portion of the gate rotor; g. the hub portion of the main rotor having a recess adjacent the said first flank of the main rotor tooth to permit passage of the gate rotor tooth; h. the hub portion of the gate rotor having a recess adjacent the concave flank to permit passage of the main rotor tooth; i. the substantially constant hub radius of the main rotor hub portion being shorter than the substantially constant hub radius of the gate rotor hub portion; j. said gate rotor hub portion being effective to control an axial port in the end wall of the gate rotor bore; k. said port acting as a high pressure port and being substantially arc shaped and extending along a sweep of at least 60* and radially to a distance shorter than the gate rotor hub portion to provide a sealing means around said port during the portion of the gate rotor revolution when the port is closed by the gate rotor hub portion;
 1. the constant radius portion of the main rotor extending about a sweep between 180* and 250* of its pitch circle; M. the second flank of the main rotor comprising a convex flank portion and a substantially straight portion which is tangent to the constant radius hub portion and said convex flank portion which extends substantially to the maximum radius of the main rotor tooth, n. the rotors having such profiles as to seal the bores and the end walls of the casing during the main part of each revolution and so as to cause the concave flank of the gate rotor tooth and said recess defining convex and concave contour portions to be generated by said main rotor tooth and the convex flank thereof along a sweep of substantially 90* of the periphery of the gate rotor, the concave flank of the gate rotor tooth and said convex and concave contours forming together combined concave and convex contour portions having a single inflection point.
 2. A rotary piston machine according to claim 1, in which the profiles of said rotors being calibrated so that a compressed fluid space communicating with the high pressure port will be located between the concave flank of the gate rotor tooth and the convex flank of the main rotor tooth when the teeth interengage and said sealing lines move and until the sealing lines intersect, whereby the torque of the fluid pressure acting on said rotors during each revolution is maintained in the same direction during a complete working cycle of the machine.
 3. A rotary piston machine according to claim 1 in which the gate rotor tooth comprises a straight portion which is tangent to the constant radius hub portion and merges with the leading flank of the gate rotor tooth through an arcuate portion forming the maximum radius of the gate rotor tooth.
 4. A rotary piston machine according to claim 3 in which the gate rotor hub recess comprises a first concave portion which forms an envelope for the ends of the radii of a family of circles generated by the convex flank portion of the main rotor tooth, and a second convex portion which is generated by the movement of the tangent point between the straight portion of the main rotor tooth and said convex portion of the gate rotor hub recess.
 5. A rotary piston machine according to claim 3 in which the port acting as high pressure port is substantially arc shaped and extends along a sweep of at least 60*;is confined radially substantially by a first outer arc disposed at a distance from the rotor axis which is shorter than the gate rotor hub portion radius to provide an outer axial sealing area along said port during the portion of the gate rotor revolution when the port is closed by the gate rotor hub portion and a second inner arc disposed at a distance from the rotor axis which is larger than the radius of the rotor shaft and provides an inner axial sealing area broader than said outer axial sealing area, said high pressure port being confined at one end by an edge along a line substantially defined by the tip of the main rotor tooth during a substantial portion of its sweep along the concave rotor tooth flank. 